I bought my miso paste at a Korean grocery store. It comes in a wee box, I think it's red miso paste. Use a pot of water, fill it halfway then use about 2 to 3 tbsp of the paste then (and this is VERY IMPORTANT) add in the Bonito fish flakes flavoring. It's the stuff that gives the miso its flavor. I've tried making miso without it and it just sucks.
Use only a little sprinkle of the flavoring as too much will make it very salty. Then I add silky tofu pieces to the broth. Just before serving into invididual bowls, I add some wakame seaweed and chopped green onions.